<template>
  <div class="music-list">
    <div class="back" @click="back">
      <i class="icon-back"></i>
    </div>
    <h1 class="title" v-html="title"></h1>
    <div class="bg-image" :style="bgStyle" ref="bgImage">
      <div class="play-wrapper">
        <div ref="playBtn" class="play" v-show="songs.length>0"
                            @click="random">
          <i class="icon-play"></i>
          <span class="text">随机播放全部</span>
        </div>
      </div>
      <div class="filter" ref="filter"></div>
    </div>
    <div class="bg-layer" ref="layer"></div>
    <scroll :data="songs"
              @scroll="scroll"
             :listen-scroll="listenScroll"
             :probe-type="probeType"
            class="list" ref="list">
      <div class="song-list-wrapper">
        <song-list :songs="songs" @select="selectItem"></song-list>
      </div>
      <div v-show="!songs.length" class="loading-container">
        <loading></loading>
      </div>
    </scroll>
  </div>
</template>

<script type="text/ecmascript-6">
  import Scroll from '../../base/scroll/scroll.vue';
  import Loading from '../../base/loading/loading.vue'
  import SongList from '../../base/song-list/song-list.vue'
  import {prefixStyle} from '../../common/js/dom'
  import {mapActions} from 'vuex'
  import {playlistMixin} from '../../common/js/mixin'

  const RESERVED_HEIGHT=40;
  const transform = prefixStyle('transform');
  const backdrop=prefixStyle('backdrop-filter');

  export default{
      mixins:[playlistMixin],
      props:{
          bgImage:{
              type:String,
              default:''
          },
          songs:{
              type:Array,
              default:[]
          },
          title:{
              type:String,
              default:''
          }
      },
      data(){
          return{
              scrollY:0
          }
      },
      //computed相当于属性的一个实时计算，如果实时计算里关联了对象，那么当对象的某个值改变的时候，同事会出发实时计算。
      computed:{
          bgStyle(){
              return `background-image:url(${this.bgImage})`
          }
      },
      //created 这个钩子在实例被创建之后被调用
      created(){
          this.probeType=3;
          this.listenScroll=true
      },
      mounted(){
          this.imageHeight=this.$refs.bgImage.clientHeight;
          this.minTransalteY=-this.imageHeight+RESERVED_HEIGHT;
          this.$refs.list.$el.style.top=`${this.imageHeight}px`
      },
      methods:{
          handlePlaylist(playlist){
            const bottom=playlist.length>0?'60px':''
            this.$refs.list.$el.style.bottom=bottom;
            this.$refs.list.refresh();
          },
          scroll(pos){
              this.scrollY=pos.y
          },
          back(){
              this.$router.back()
          },
          selectItem(item,index){
            this.selectPlay({
              list:this.songs,
              index
            })
          },
        random(){
          this.randomPlay({
            list:this.songs
          })
        },
        ...mapActions([
            'selectPlay',
            'randomPlay'
        ])
      },
      watch:{
          scrollY(newVal){
              let translateY=Math.max(this.minTransalteY,newVal);
              let scale=1;
              let zIndex=0;
              let blur=0;
              const percent=Math.abs(newVal/this.imageHeight);
              if(newVal>0){
                  scale=1+percent;
//                  console.log(scale);
                    zIndex=10;
              }else{
                  blur=Math.min(20,percent*20);
              }

              this.$refs.layer.style[transform]=`translate3d(0,${translateY}px,0)`;
              //backdrop 用于ios 线性模糊
              this.$refs.filter.style[backdrop]=`blur(${blur}px)`;
              //向上拉
              if(newVal<this.minTransalteY){
                  zIndex=10;
                  this.$refs.bgImage.style.paddingTop=0;
                  this.$refs.bgImage.style.height=`${RESERVED_HEIGHT}px`;
                  this.$refs.playBtn.style.display='none';
              }else{
                  this.$refs.bgImage.style.paddingTop='70%';
                  this.$refs.bgImage.style.height=0;
                this.$refs.playBtn.style.display='';
              }
              this.$refs.bgImage.style[transform]=`scale(${scale})`;
              this.$refs.bgImage.style.zIndex=zIndex
          }
      },
      components:{
          Scroll,
          SongList,
          Loading
      }
  }

</script>

<style scoped lang="stylus" rel="stylesheet/stylus">
  @import "~common/stylus/variable"
  @import "~common/stylus/mixin"

  .music-list
    position: fixed
    z-index: 100
    top: 0
    left: 0
    bottom: 0
    right: 0
    background: $color-background
    .back
      position absolute
      top: 0
      left: 6px
      z-index: 50
      .icon-back
        display: block
        padding: 10px
        font-size: $font-size-large-x
        color: $color-theme
    .title
      position: absolute
      top: 0
      left: 10%
      z-index: 40
      width: 80%
      no-wrap()
      text-align: center
      line-height: 40px
      font-size: $font-size-large
      color: $color-text
    .bg-image
      position: relative
      width: 100%
      height: 0
      padding-top: 70%
      transform-origin: top
      background-size: cover
      .play-wrapper
        position: absolute
        bottom: 20px
        z-index: 50
        width: 100%
        .play
          box-sizing: border-box
          width: 135px
          padding: 7px 0
          margin: 0 auto
          text-align: center
          border: 1px solid $color-theme
          color: $color-theme
          border-radius: 100px
          font-size: 0
          .icon-play
            display: inline-block
            vertical-align: middle
            margin-right: 6px
            font-size: $font-size-medium-x
          .text
            display: inline-block
            vertical-align: middle
            font-size: $font-size-small
      .filter
        position: absolute
        top: 0
        left: 0
        width: 100%
        height: 100%
        background: rgba(7, 17, 27, 0.4)
    .bg-layer
      position: relative
      height: 100%
      background: $color-background
    .list
      position: fixed
      top: 0
      bottom: 0
      width: 100%
      background: $color-background
      .song-list-wrapper
        padding: 20px 30px
      .loading-container
        position: absolute
        width: 100%
        top: 50%
        transform: translateY(-50%)
</style>
